CN114665056B - High-compaction-density lithium iron phosphate positive electrode plate and preparation method thereof - Google Patents
High-compaction-density lithium iron phosphate positive electrode plate and preparation method thereof Download PDFInfo
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- CN114665056B CN114665056B CN202210185387.7A CN202210185387A CN114665056B CN 114665056 B CN114665056 B CN 114665056B CN 202210185387 A CN202210185387 A CN 202210185387A CN 114665056 B CN114665056 B CN 114665056B
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- iron phosphate
- lithium iron
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 70
- 238000005056 compaction Methods 0.000 title claims abstract description 32
- 238000002360 preparation method Methods 0.000 title abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 35
- 229910052799 carbon Inorganic materials 0.000 claims description 33
- 238000005245 sintering Methods 0.000 claims description 18
- 239000002245 particle Substances 0.000 claims description 17
- 239000006258 conductive agent Substances 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 12
- 239000007774 positive electrode material Substances 0.000 claims description 12
- 239000006230 acetylene black Substances 0.000 claims description 11
- 239000013543 active substance Substances 0.000 claims description 10
- 239000010405 anode material Substances 0.000 claims description 10
- 239000011248 coating agent Substances 0.000 claims description 10
- 238000000576 coating method Methods 0.000 claims description 10
- 239000002033 PVDF binder Substances 0.000 claims description 9
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 9
- 239000000853 adhesive Substances 0.000 claims description 8
- 230000001070 adhesive effect Effects 0.000 claims description 8
- 229920000642 polymer Polymers 0.000 claims description 7
- 238000004537 pulping Methods 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 7
- 238000007873 sieving Methods 0.000 claims description 7
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 6
- 239000008103 glucose Substances 0.000 claims description 6
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 6
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 6
- 239000002002 slurry Substances 0.000 claims description 6
- 238000000967 suction filtration Methods 0.000 claims description 6
- 239000002243 precursor Substances 0.000 claims description 5
- 238000001694 spray drying Methods 0.000 claims description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 239000005955 Ferric phosphate Substances 0.000 claims description 3
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- 229940032958 ferric phosphate Drugs 0.000 claims description 3
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 3
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 3
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- 238000005507 spraying Methods 0.000 claims description 3
- 238000001238 wet grinding Methods 0.000 claims description 3
- -1 and pulping Substances 0.000 claims description 2
- 150000002085 enols Chemical class 0.000 claims 1
- 238000000034 method Methods 0.000 abstract description 8
- 230000000052 comparative effect Effects 0.000 description 11
- 239000011230 binding agent Substances 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- 239000011149 active material Substances 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 4
- 241000872198 Serjania polyphylla Species 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- 229910052698 phosphorus Inorganic materials 0.000 description 4
- 239000011574 phosphorus Substances 0.000 description 4
- 239000006245 Carbon black Super-P Substances 0.000 description 3
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 230000010355 oscillation Effects 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 description 2
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 229910001386 lithium phosphate Inorganic materials 0.000 description 2
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 2
- 239000005011 phenolic resin Substances 0.000 description 2
- 229920001568 phenolic resin Polymers 0.000 description 2
- 229920001223 polyethylene glycol Polymers 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 2
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 1
- 229930006000 Sucrose Natural products 0.000 description 1
- MCDLETWIOVSGJT-UHFFFAOYSA-N acetic acid;iron Chemical compound [Fe].CC(O)=O.CC(O)=O MCDLETWIOVSGJT-UHFFFAOYSA-N 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- 239000011668 ascorbic acid Substances 0.000 description 1
- 229960005070 ascorbic acid Drugs 0.000 description 1
- 235000010323 ascorbic acid Nutrition 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229960004887 ferric hydroxide Drugs 0.000 description 1
- 229940062993 ferrous oxalate Drugs 0.000 description 1
- 229910021389 graphene Inorganic materials 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 description 1
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 1
- YPJCVYYCWSFGRM-UHFFFAOYSA-H iron(3+);tricarbonate Chemical compound [Fe+3].[Fe+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O YPJCVYYCWSFGRM-UHFFFAOYSA-H 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 229920000767 polyaniline Polymers 0.000 description 1
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 1
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 1
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000005720 sucrose Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical Kinetics & Catalysis (AREA)
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- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a high-compaction-density lithium iron phosphate positive electrode plate and a preparation method thereof, and specifically relates to a preparation method of the high-compaction-density lithium iron phosphate positive electrode plate. The lithium iron phosphate material prepared by the method has higher conductivity and tap density and lower specific surface area.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a high-compaction-density lithium iron phosphate positive electrode plate and a preparation method thereof.
Background
With the large-scale application of lithium ion batteries, the quality of the positive electrode material is directly related to the development of the lithium ion battery industry as the most core component of lithium ions. The lithium iron phosphate positive electrode material has been widely concerned with the advantages of stable working voltage, long cycle life, good safety performance and the like, but the low compaction density of the lithium iron phosphate limits the improvement of the energy density of the battery of the positive electrode material system.
The compaction density of the positive pole piece has close relation with the capacity, internal resistance and other performances of the battery. The compacted density is related not only to the size of the particles, tap density, but also to the content of coated carbon. Generally, the higher the compacted density of the positive electrode sheet, the higher the capacity of the battery. Therefore, proper improvement of the compacted density of the positive electrode sheet is important to the design of the lithium ion battery.
The method for improving the compaction density of the lithium iron phosphate anode is mainly two, namely (1) the method for improving the tap density of the lithium iron phosphate material is carried out, and the material and the particles are graded; chinese patent CN108011104A discloses a high-compaction-density lithium iron phosphate anode material and a preparation method thereof, wherein the patent selects slurry of two particles with different sizes, and the slurry is mixed after being dried and sintered at high temperature respectively to obtain the lithium iron phosphate anode material with larger compaction density. (2) Modifying the binder and the conductive agent, reducing the consumption of the conductive agent or the binder, reducing the specific surface area of the surface of the pole piece, improving the surface density and further improving the compaction density; chinese patent CN110544769 a discloses a method for preparing a high-compaction lithium iron phosphate positive electrode sheet, in which a carbon source binder and a lithium iron phosphate material are mixed into slurry, coated, passed through a roller and calcined under a protective atmosphere, and the sheet is cooled and then placed in a dimethylformamide solution of polyvinylidene fluoride for infiltration, taken out and dried. The lithium iron phosphate positive electrode material in the positive electrode plate prepared by the method has the advantages that the ratio of the lithium iron phosphate positive electrode material is high, a high-density structure is formed in the rolling process, micropores formed after carbonization of the carbon source binder in the heat treatment process are uniformly distributed among particles, electrolyte infiltration is facilitated, a 3D carbon network formed in the process plays a certain adhesive role, and the finally prepared lithium iron phosphate positive electrode plate has a high density.
In summary, developing a compacted density lithium iron phosphate positive electrode sheet has important significance for the development of lithium ion batteries.
Disclosure of Invention
Aiming at the problem that the energy density of a battery of a positive electrode material system is limited to be improved due to the low compaction density of lithium iron phosphate in the prior art, the invention provides a high compaction density lithium iron phosphate positive electrode plate and a preparation method thereof.
The invention is realized by the following technical scheme:
the high-compaction-density lithium iron phosphate positive electrode plate is prepared by the following method:
(1) Mixing a lithium source, an iron source, a phosphorus source and a carbon source in proportion, grinding and refining, spray drying to obtain a precursor, and sintering at high temperature under a protective atmosphere to obtain a low-carbon lithium iron phosphate anode material;
(2) Mixing the low-carbon lithium iron phosphate anode material obtained in the step (1) with a high polymer carbon source in a solvent, performing suction filtration and drying after ultrasonic oscillation, sieving the dried material, and performing secondary sintering to obtain a secondary coated lithium iron phosphate material;
(3) And (3) taking the secondarily-coated lithium iron phosphate material obtained in the step (2) as an active substance and acetylene black as a conductive agent, adding a binder, coating, drying and passing through a roller to obtain the high-compaction-density lithium iron phosphate positive electrode plate.
Further, in the step (1), the molar ratio of the lithium source, the iron source and the phosphorus source is 1.02:1:1, the addition amount of the carbon source accounts for 3-4% of the total mass of the raw materials in the step (1); the mass ratio of the low-carbon lithium iron phosphate anode material to the high polymer carbon source in the step (2) is 10:1.
further, the mass ratio of the secondary coated lithium iron phosphate material, the acetylene black and the binder in the step (3) is 85.2-85.4: 13:1.6 to 1.8.
Further, in the step (1), the sintering temperature is 650-750 ℃ and the sintering time is 5-7 h; in the step (2), the secondary sintering temperature is 600-700 ℃ and the sintering time is 5-7 h.
Further, the solvent in the step (2) is water, the ultrasonic wave is 30 MHz, the oscillation time is 1-5 h, the drying temperature is 150 ℃, and the particle size of the secondarily coated lithium iron phosphate material obtained through sieving is 700-1000 nm.
Further, the lithium source in the step (1) is one or more of lithium carbonate, lithium acetate, lithium hydroxide, lithium dihydrogen phosphate and lithium phosphate, the iron source is one or more of ferric hydroxide, ferric phosphate, ferrous acetate, ferric carbonate, ferric oxide and ferrous oxalate, the phosphorus source is one or more of lithium dihydrogen phosphate, ammonium dihydrogen phosphate and lithium phosphate, and the carbon source is one or more of glucose, citric acid, ascorbic acid, sucrose, carbon black, acetylene black, carbon nanotubes and graphene; the carbon source in the step (2) is more than one of polyvinyl alcohol, polyethylene glycol, polyethylene oxide, phenolic resin, polyaniline and polyvinylpyrrolidone.
Further, the particle size of the acetylene black in the step (3) is 30-50 nm, and the binder is polyvinylidene fluoride.
The preparation method of the high-compaction-density lithium iron phosphate positive electrode plate comprises the following steps:
(1) Mixing a lithium source, an iron source, a phosphorus source and a carbon source in proportion, grinding and refining, spray drying to obtain a precursor, and sintering at high temperature under a protective atmosphere to obtain a low-carbon lithium iron phosphate anode material;
(2) Mixing the low-carbon lithium iron phosphate anode material obtained in the step (1) with a high polymer carbon source in a solvent, performing suction filtration and drying after ultrasonic oscillation, sieving the dried material, and performing secondary sintering to obtain a secondary coated lithium iron phosphate material;
(3) And (3) taking the secondarily-coated lithium iron phosphate material obtained in the step (2) as an active substance and acetylene black as a conductive agent, adding a binder, coating, drying and passing through a roller to obtain the high-compaction-density lithium iron phosphate positive electrode plate.
Advantageous effects
(1) The lithium iron phosphate material with the average particle size of 700-1000 nm and the surface provided with the carbon coating layer in a film form has higher conductivity and tap density, and simultaneously has lower specific surface area, the use amount of the conductive agent can be reduced by the higher conductivity, the powder compaction density of the material is improved by the higher tap density, and the use amount of the binder can be reduced by the lower specific surface area;
(2) According to the invention, 30-50 nm acetylene black is used as a conductive agent to fill gaps among active substances, so that the compaction density of the positive plate can be improved. Experiments show that the final compaction density is 2.8g/cm 3 Lithium iron phosphate positive electrode plate.
Drawings
Fig. 1 is a first charge-discharge curve of the high-compaction density lithium iron phosphate positive electrode sheet prepared in example 1 at a rate of 0.2C.
Detailed Description
The following description of the embodiments of the present invention will be made in detail, but not to limit the scope of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
(1) Iron phosphate and lithium carbonate were mixed according to 4:1, then adding glucose as a carbon source, wherein the total mass of raw materials (ferric phosphate, lithium carbonate and glucose) is 1200g, the addition amount of the carbon source accounts for 3wt% of the total mass of the raw materials, carrying out wet grinding for 4 hours, carrying out spray drying on the ground slurry, adopting a pneumatic spray dryer, wherein the pressure during spraying is 0.36Mpa, sintering the dried precursor in a tube furnace at 740 ℃ for 5 hours under the nitrogen atmosphere, and cooling to room temperature to obtain a low-carbon lithium iron phosphate anode material LFP1;
(2) Adding 500g of the low-carbon lithium iron phosphate cathode material LFP1 obtained in the step (1) and 50g of polyvinyl alcohol high polymer into 500ml of deionized water, performing ultrasonic vibration for 2 hours in an ultrasonic container with ultrasonic wave of 30 MHz, performing suction filtration, baking in an oven at 150 ℃ for 1 hour, sieving the dried material to obtain a particle size of 700-1000 nm, performing secondary sintering at the sintering temperature of 700 ℃ for 6 hours to obtain a secondary coated lithium iron phosphate material LFP2;
(3) 426g of secondary coated lithium iron phosphate material LFP2 prepared in the step (2) is taken as an active substance, 65g of acetylene black with the particle size of 30-50 nm is taken as a conductive agent, 9g of PVDF is taken as an adhesive, and after pulping, coating, drying and roller passing, a high-compaction-density lithium iron phosphate positive electrode plate J1 is obtained, wherein a primary charge-discharge curve at 0.2C is shown as a graph in fig. 1, and the lithium iron phosphate positive electrode plate J1 still has 161mAh g on the premise of improving compaction density -1 Is a discharge capacity of (a).
Example 2
(1) Step (1) is the same as in example 1;
(2) Adding 500g of the low-carbon lithium iron phosphate cathode material LFP1 obtained in the step (1) and 50g of polyethylene glycol high polymer into 500ml of deionized water, performing ultrasonic vibration in an ultrasonic container with ultrasonic waves of 30 MHz for 2 hours, performing suction filtration, baking in an oven with the temperature of 150 ℃ for 1 hour, sieving the dried material to obtain a particle size of 700-1000 nm, performing secondary sintering at the sintering temperature of 700 ℃ for 6 hours, and obtaining a secondary coated lithium iron phosphate material LFP3;
(3) 426g of the secondary coated lithium iron phosphate material LFP3 prepared in the step (2) is used as an active substance, 65g of acetylene black with the particle size of 30-50 nm is used as a conductive agent, 9g of PVDF is used as an adhesive, and the high-compaction density lithium iron phosphate positive electrode J2 is obtained after pulping, coating, drying and passing through a roller.
Example 3
(1) Step (1) is the same as in example 1;
(2) Adding 500g of the low-carbon lithium iron phosphate positive electrode material LFP1 obtained in the step (1) and 50g of phenolic resin high polymer into 500ml of deionized water, performing ultrasonic vibration in an ultrasonic container with ultrasonic waves of 30 MHz for 2 hours, performing suction filtration, baking in an oven with the temperature of 150 ℃ for 1 hour, sieving the dried material to obtain a particle size of 700-1000 nm, performing secondary sintering at the sintering temperature of 700 ℃ for 6 hours, and obtaining a secondary coated lithium iron phosphate material LFP4;
(3) 426g of the secondary coated lithium iron phosphate material LFP4 prepared in the step (2) is used as an active substance, 65g of acetylene black with the particle size of 30-50 nm is used as a conductive agent, 9g of PVDF is used as an adhesive, and the high-compaction density lithium iron phosphate positive electrode J3 is obtained after pulping, coating, drying and passing through a roller.
Comparative example 1
(1) Iron phosphate and lithium carbonate were mixed according to 4: mixing with a mass ratio of 1, adding glucose as a carbon source, wherein the total mass of the raw materials is 1200g, the addition amount of the carbon source accounts for 3wt% of the total mass of the raw materials, carrying out wet grinding for 4 hours, carrying out spray drying on the ground slurry, adopting a pneumatic spray dryer, wherein the pressure is 0.36Mpa during spraying, sintering the dried precursor in a tube furnace at 740 ℃ for 5 hours under the nitrogen atmosphere, and cooling to room temperature to obtain a lithium iron phosphate anode material LFP5;
(2) 426g of the lithium iron phosphate positive electrode material LFP5 prepared in the step (1) is used as an active substance, 65g of acetylene black with the particle size of 30-50 nm is used as a conductive agent, 9g of PVDF is used as an adhesive, and the high-compaction density lithium iron phosphate positive electrode plate J4 is obtained after pulping, coating, drying and roller passing.
Comparative example 2
(1) Step (1) is the same as step (1) of example 1;
(2) Step (2) is the same as step (2) of example 1;
(3) 426g of the lithium iron phosphate positive electrode material LFP2 prepared in the step (1) is used as an active substance, 65g of Super-P with the particle size of 30-40 nm is used as a conductive agent, 9g of PVDF is used as an adhesive, and the high-compaction density lithium iron phosphate positive electrode plate J5 is obtained after pulping, coating, drying and passing through a roller.
Comparative example 3
(1) Step (1) is the same as step (1) of example 1;
(2) Step (2) is the same as step (2) of example 1;
(3) 426g of the lithium iron phosphate positive electrode material LFP2 prepared in the step (1) is used as an active substance, 75g of Super-P with the particle size of 30-40 nm is used as a conductive agent, 9g of PVDF is used as an adhesive, and the high-compaction density lithium iron phosphate positive electrode plate J6 is obtained after pulping, coating, drying and passing through a roller.
Performance testing
(1) The specific surface area and tap density of the carbon-coated lithium iron phosphate positive electrode materials LFP2, LFP3, LFP4 and LFP5 prepared in examples 1 to 3 and comparative examples 1 to 3 were tested, and the results are shown in table 1 below, and it can be seen from table 1 that the secondary-coated lithium iron phosphate material has a lower specific surface area and a higher tap density, and the lower specific surface area reduces the contact area between the active material and the active material, and between the active material and the pole piece, and reduces the amount of binder. Whereas higher tap density is one of the important factors for higher compacted density, comparative example 1 has no regular film-like carbon coating layer but a higher specific surface area and a lower tap density;
table 1 specific surface area, tap density of lithium iron phosphate materials of examples and comparative examples
。
(2) The compacted densities, internal resistances, and specific capacities of the lithium iron phosphate pole pieces J1, J2, J3, J4, J5, and J6 prepared in examples 1 to 3 and comparative examples 1 to 3 were measured, and the measurement results are shown in table 2 below:
as can be seen from Table 2, J1-3 all have higher compaction density, while the three examples also have lower internal resistance and higher gram capacity due to the thin film-like highly conductive carbon coating of the active material. Comparative example 1 has a higher internal resistance due to insufficient conductivity of the clad layer, and a lower tap density results in a lower compacted density. The Super-P used in comparative example 2 did not sufficiently fill the gaps between the active materials, resulting in a pole piece having a lower compacted density and higher internal resistance. Although the internal resistance of the pole piece of comparative example 3 is lower, the compaction density of the pole piece is higher due to the more conductive agent used;
TABLE 2 compacted density, internal resistance, specific Capacity of lithium iron phosphate Pole pieces of examples and comparative examples
。
Claims (1)
1. A high compaction density lithium iron phosphate positive plate is characterized in that:
(1) Iron phosphate and lithium carbonate were mixed according to 4:1, adding glucose as a carbon source, wherein the total mass of raw materials of ferric phosphate, lithium carbonate and glucose is 1200g, the adding amount of the carbon source accounts for 3wt% of the total mass of the raw materials, carrying out wet grinding for 4h, carrying out spray drying on the ground slurry, adopting a pneumatic spray dryer, wherein the pressure during spraying is 0.36Mpa, sintering the dried precursor in a tube furnace at 740 ℃ for 5h under the nitrogen atmosphere, and cooling to room temperature to obtain the low-carbon lithium iron phosphate anode material;
(2) 500g of the low-carbon lithium iron phosphate positive electrode material obtained in the step (1) and 50g of polyethyleneAdding enol polymer into 500ml deionized water, performing ultrasonic vibration in an ultrasonic container with ultrasonic wave of 30 MHz for 2 hours, performing suction filtration, baking in an oven at 150 ℃ for 1 hour, sieving the baked material to obtain a particle size of 700-1000 nm, performing secondary sintering at 700 ℃ for 6 hours to obtain a secondary coated lithium iron phosphate material with a specific surface area of 8.6m 2 Per gram, tap density of 1.63g/cm 3 ；
(3) Taking 426g of the secondarily coated lithium iron phosphate material prepared in the step (2) as an active substance, 65g of 30-50 nm acetylene black as a conductive agent and 9g of PVDF as an adhesive, and pulping, coating, drying and passing through rollers to obtain a compact density of 2.82g/cm 3 Lithium iron phosphate positive electrode plate.
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| CN102009970A (en) * | 2010-11-22 | 2011-04-13 | 湖南杉杉新材料有限公司 | Method for preparing high-density lithium ferric phosphate |
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